已知数列{an}的前n项和为Sn,且对任意正整数n,有Sn,a/2(a-1),n(a不等于0,a不等于1)成等差数列,令bn=(an +(1)求{an}的通项公式an.(用n,a表示)(2)当a=8/9时.数列{bn}是否存在最小项,若有,请求出第几
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![已知数列{an}的前n项和为Sn,且对任意正整数n,有Sn,a/2(a-1),n(a不等于0,a不等于1)成等差数列,令bn=(an +(1)求{an}的通项公式an.(用n,a表示)(2)当a=8/9时.数列{bn}是否存在最小项,若有,请求出第几](/uploads/image/z/6799837-13-7.jpg?t=%E5%B7%B2%E7%9F%A5%E6%95%B0%E5%88%97%7Ban%7D%E7%9A%84%E5%89%8Dn%E9%A1%B9%E5%92%8C%E4%B8%BASn%2C%E4%B8%94%E5%AF%B9%E4%BB%BB%E6%84%8F%E6%AD%A3%E6%95%B4%E6%95%B0n%2C%E6%9C%89Sn%2Ca%2F2%28a-1%29%2Cn%28a%E4%B8%8D%E7%AD%89%E4%BA%8E0%2Ca%E4%B8%8D%E7%AD%89%E4%BA%8E1%29%E6%88%90%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%2C%E4%BB%A4bn%3D%28an+%EF%BC%8B%EF%BC%881%EF%BC%89%E6%B1%82%7Ban%7D%E7%9A%84%E9%80%9A%E9%A1%B9%E5%85%AC%E5%BC%8Fan.%28%E7%94%A8n%2Ca%E8%A1%A8%E7%A4%BA%29%EF%BC%882%EF%BC%89%E5%BD%93a%3D8%EF%BC%8F9%E6%97%B6.%E6%95%B0%E5%88%97%7Bbn%7D%E6%98%AF%E5%90%A6%E5%AD%98%E5%9C%A8%E6%9C%80%E5%B0%8F%E9%A1%B9%2C%E8%8B%A5%E6%9C%89%2C%E8%AF%B7%E6%B1%82%E5%87%BA%E7%AC%AC%E5%87%A0)
已知数列{an}的前n项和为Sn,且对任意正整数n,有Sn,a/2(a-1),n(a不等于0,a不等于1)成等差数列,令bn=(an +(1)求{an}的通项公式an.(用n,a表示)(2)当a=8/9时.数列{bn}是否存在最小项,若有,请求出第几
已知数列{an}的前n项和为Sn,且对任意正整数n,有Sn,a/2(a-1),n(a不等于0,a不等于1)成等差数列,令bn=(an +
(1)求{an}的通项公式an.(用n,a表示)
(2)当a=8/9时.数列{bn}是否存在最小项,若有,请求出第几项.
(3)若{bn}是一个单调递增数列,请求出a的取值范围.
每一问都要.
这才是正确题目。。。刚打错了
已知数列{an}的前n项和为Sn,且对任意正整数n,有Sn,a/2(a-1)*an,n(a不等于0,a不等于1)成等差数列令bn=(an +1)*lg(an +1)。
已知数列{an}的前n项和为Sn,且对任意正整数n,有Sn,a/2(a-1),n(a不等于0,a不等于1)成等差数列,令bn=(an +(1)求{an}的通项公式an.(用n,a表示)(2)当a=8/9时.数列{bn}是否存在最小项,若有,请求出第几
(1)Sn,a/2(a-1),n(a不等于0,a不等于1)成等差数列,则2×a/2(a-1)=Sn+n,即Sn=a/(a-1)-n
则Sn-1=a/(a-1)-(n-1),则an=Sn-Sn-1=-1.
是不是题目出错了还是输入错误,请楼主再检查一下!
Sn,a/2(a-1),n(a不等于0,a不等于1)成等差数列,则2×a/2(a-1)=Sn+n,即Sn=a/(a-1)-n
则Sn-1=a/(a-1)-(n-1),则an=Sn-Sn-1=-1
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